1. Field of the Invention
The present invention relates generally to medical devices, kits, and methods. More particularly, the present invention relates to systems and procedures for crossing chronic total occlusions in blood vessels with guidewires and subsequently performing angioplasty, atherectomy, stenting, or other treatments.
Cardiovascular disease is a leading cause of mortality worldwide. Cardiovascular disease can take many forms, and a variety of specific interventional and pharmaceutical treatments have been devised over the years with varying levels of success.
A particularly troublesome form of cardiovascular disease results when a blood vessel becomes totally occluded with atheroma or plaque, referred to as a chronic total occlusion. Until recently, chronic total occlusions have usually been treated by performing a bypass procedure where an autologous or synthetic blood vessel is anastomotically attached to locations on the blood vessel upstream and downstream of the occlusion. While highly effective, such bypass procedures are quite traumatic to the patient.
Recently, catheter-based intravascular procedures have been utilized to treat chronic total occlusions with increasing success. Catheter-based intravascular procedures include angioplasty, atherectomy, stenting, and the like, and are often preferred because they are much less traumatic to the patient. Before such catheter-based treatments can be performed, however, it is usually necessary to cross the occlusion with a guidewire to provide access for the interventional catheter. In some instances, crossing the occlusion with a guidewire can be accomplished simply by pushing the guidewire through the occlusion. The guidewire remains in the blood vessel lumen and provides the desired access path. In many cases, however, the guidewire inadvertently penetrates into the subintimal space between the intimal layer and the adventitial layer of the blood vessel as it attempts to cross the occlusion. Once in the subintimal space, it is very difficult and in many cases impossible to direct the guidewire back into the blood vessel lumen. In such cases, it will usually be impossible to perform the catheter-based intervention and other, more traumatic, procedures may have to be employed.
For these reasons, it would be desirable to provide methods, kits, and apparatus which facilitate crossing a chronic total occlusion in a blood vessel with a guidewire. In particular, it would be desirable to provide catheters, guides, or other apparatus which could be used with a conventional or specialized guidewire to direct or redirect the guidewire from the subintimal space back into the blood vessel lumen after the guidewire has entered such space. Such methods and apparatus should be useful in coronary arteries as well as other blood vessels and should be capable of being performed with or without imaging from within or adjacent to the blood vessel. The apparatus for achieving these objective should be of simple construction and be capable of being used in a straight-forward, generally fool-proof manner. At least some of these objectives will be met by the invention described hereinafter.
2. Description of the Background Art
Catheters having side guidewire entry ports spaced proximally from their distal tips are described in U.S. Pat. Nos. 5,464,395; 5,413,581; 5,190,528; 5,183,470; 4,947,864; and 4,405,314. Catheters and methods for forming lateral penetrations through tissue to and from blood vessels past total occlusions are described in U.S. Pat. Nos. 5,443,497; 5,429,144; 5,409,019; 5,287,861; WO 97/13463; and WO 97/13471.
According to the present invention, methods are provided for crossing total occlusions in blood vessels. While the methods are particularly beneficial for the treatment of coronary artery disease, they are also useful in the treatment of other arteries and veins, such as the treatment of peripheral vascular diseases.
The total occlusions are crossed by first forming a track from a lumen in the blood vessel into a subintimal space between an intimal layer and an adventitial layer of the blood vessel. The track is formed so that it extends from a location proximal of the total occlusion to a location which is distal to the total occlusion. A passage is then formed from the track back into the blood vessel lumen at the distal location. In the specific embodiments, the track is formed by advancing a wire through the blood vessel lumen into the subintimal space, typically by advancing the wire until it encounters the total occlusion. By continuing to advance the wire, it will usually pass into the subintimal space and can be further advanced to the desired distal location. After the wire is located distally to the total occlusion, it is typically deflected from the track back into the blood vessel lumen.
In the exemplary methods, the wire is deflected using a deflecting catheter. Typically, the deflecting catheter is advanced over a proximal end of the wire and advanced into the track within the subintimal space. The wire and the deflecting catheter are then manipulated so that the wire is deflected laterally through the intimal layer back into the blood vessel lumen. Such deflecting catheters are also useful in supporting the wire as it is advanced into and/or through the track, i.e. the catheter can enhance the xe2x80x9cpushabilityxe2x80x9d of the wire when it is advanced forward through any resisting material. Specific designs for such deflecting catheters are described in detail below. Alternatively, the wire which is initially positioned within the track in the subintimal space may be withdrawn through the deflecting catheter and exchanged for a second wire or other device suitable for penetrating through the intimal layer back into the blood vessel lumen. It will be appreciated that the wires and/or deflecting and other catheters may be freely exchanged over or through one another in a conventional matter without departing from the present invention.
It will usually be necessary to determine when the wire and/or deflecting catheter are positioned distal to the total occlusion so that the wire may be returned to the blood vessel lumen beyond said occlusion. Most simply, such position determination can be made by fluoroscopically imaging the blood vessel in a conventional manner. Alternatively or additionally to such fluoroscopic imaging, intravascular imaging, e.g. intravascular ultrasonic imaging (IVUS), and a variety of optical imaging modelities, such as optical coherence tomography (OCT), may be employed. For example, an ultrasonic imaging guidewire may be used to initially access the subintimal space and/or may be exchanged for the wire which is used to access the subintimal space. An imaging guidewire present in the subintimal space may readily detect the presence or absence of occluding material within the blood vessel lumen. When the transition from occluding material to lack of occluding material is detected, it is known that the position of the guidewire has advanced beyond the total occlusion.
After the passage is formed back from the track into the blood vessel lumen and a wire is in place across the total occlusion, the wire is available for use as a guidewire in positioning interventional and diagnostic catheters across the total occlusion. Most commonly, interventional catheters will be positioned across the total occlusion for treating the occlusion. Exemplary interventional catheters include angioplasty balloon catheters, rotational atherectomy catheters, directional atherectomy catheters, stent-placement catheters, and the like.
In a preferred aspect of the methods of the present invention, the wire deflecting step will comprise deflecting a cannula from the subintimal space back into the blood vessel lumen and thereafter passing the wire through a path defined by the cannula, typically by a lumen within the cannula. Usually, the cannula will be advanced over the wire after the wire is disposed within the subintimal space, and the cannula-deflecting step will comprise advancing a resilient (pre-formed) curved end of the cannula from a constraining lumen into the blood vessel lumen. Alternatively, the wire-deflecting step may comprise advancing a deflecting catheter over the wire which has been advanced into the subintimal space. A cannula may then be advanced through a lateral opening of the deflecting catheter and penetrated through the intimal layer to define a path for the wire back into the blood vessel lumen. Steerable and other actively deployed cannulas may also be used.
The present invention further provides kits comprising a wire-deflecting catheter having a lumen or mechanism capable of laterally deflecting a wire. The kit will further comprise instructions setting forth any of the methods described above. Optionally, the kit may further comprise the wire which is used for penetrating the subintimal space and/or back into the blood vessel lumen. The kit will usually still further comprise a package for containing both the wire deflecting catheter and the instructions, and optionally the additional wire(s). Suitable packages include pouches, trays, tubes, boxes, and the like. The instructions may be printed on a separate package insert or may be printed in part or in whole on the packaging itself. Usually, the components of the kit within the package will be sterilized by conventional procedures.
Apparatus according to the present invention comprise wire-deflection systems. Exemplary wire-deflection systems usually comprise the wire-deflecting catheter which includes a catheter body and a deflecting cannula. The catheter body will have a proximal end, a distal end, and at least one lumen extending through at least a distal portion thereof. The lumen will have a distal opening and a lateral opening. The cannula also has a proximal end, a distal end, and at least one lumen extending through a distal portion thereof. The distal portion of the cannula will have a preformed, resilient curve. The cannula will be slidably disposed within the lumen of the catheter body to assume (a) a straightened configuration when the cannula is proximally retracted within the catheter body lumen and (b) a curved configuration when the cannula is extended laterally through the lateral opening of the catheter body. In this way, the cannula can be selectively deflected through the intimal layer of the blood vessel according to the preferred methods described above. The system may further comprise a wire configured to pass through the cannula lumen. The wire may be a conventional guidewire, but will more typically be a wire having a sharpened distal tip intended particularly for penetrating the intimal layer of the blood vessel wall. Optionally, the wire may further comprise an imaging means such as an ultrasonic imaging means. The catheter body will typically have a fluoroscopically visible marker near its distal end. The marker will be configured to permit visual determination of the rotational orientation of the distal end of the catheter body when viewed in a two-dimensional fluoroscopic image. The catheter body will usually be reinforced to enhance torsional rigidity, and may further comprise a distal nose cone wherein the distal and lateral openings are defined within the nose cone. The distal end of the cannula will usually be pre-formed in a smooth curve which may extend over an arc in the range from 15xc2x0 C. to 135xc2x0 C., usually from 45xc2x0 C. to 90xc2x0 C. The pre-formed curve may have a radius in the range from 0.5 mm to 15 mm, usually from 2 mm to 10 mm.